title: Metabotropic γ-aminobutyric acid (GABAB) receptors modulate feeding behavior in the calcisponge Leucandra aspera.
abstract: Here, we report the presence of the γ-aminobutyric acid (GABA)-ergic system in the calcisponge Leucandra aspera and examine the cellular localization of the components of this system, including GABA-like receptors using immunofluorescence and confocal microscopy. Furthermore, we demonstrate for the first time that GABA plays a functional role as a messenger in regulating sponge-feeding behavior. We found that both GABA(B) R1 and R2 subunits are present in the choanocytes of sponges as well as in the eso- and endopinacocytes. The functional role of GABA in the feeding behavior of this sponge was tested. The involvement of GABA receptors in the endocytic processes in L. aspera was demonstrated with dextran conjugated to Texas Red as a marker for material ingestion and by treating isolated sponge cells with a GABA(B) receptor agonist and an antagonist. The amount of dextran that was ingested increased in dissociated sponge cells when the GABA(B) receptor agonist baclofen was used, and this stimulatory effect was prevented by treatment with the GABA(B) receptor antagonist phaclofen. The baclofen effect on uptake was blocked by treatment with pertussis toxin, thus indicating a role for G proteins in modulating feeding behavior in L. aspera. Moreover, we found evidence that GABA receptors are involved in the consumption of dissolved organic matter by sponge cells. These findings suggest that GABA receptors and their functional role are highly conservative traits in the animal kingdom prenervous system evolution.
authors.affiliation: Dipartimento per lo Studio del Territorio e delle sue Risorse (DIPTERIS), Università di Genova, Genova, Italy. ramoino@dipteris.unige.it
authors.forename: Paola
authors.initials: P
authors.lastname: Ramoino
authors.forename: Fabio D
authors.initials: FD
authors.lastname: Ledda
authors.forename: Sara
authors.initials: S
authors.lastname: Ferrando
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Gallus
authors.forename: Paolo
authors.initials: P
authors.lastname: Bianchini
authors.forename: Alberto
authors.initials: A
authors.lastname: Diaspro
authors.forename: Marco
authors.initials: M
authors.lastname: Fato
authors.forename: Grazia
authors.initials: G
authors.lastname: Tagliafierro
authors.forename: Renata
authors.initials: R
authors.lastname: Manconi
mesh_terms: D000818:Animals; D001418:Baclofen / Q000031:analogs & derivatives / Q000494:pharmacology; D004347:Drug Interactions; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D058786:GABA-B Receptor Agonists / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D011161:Porifera / Q000502:physiology*; D018080:Receptors, GABA-B / Q000187:drug effects / Q000378:metabolism*
chemical_list: D018756:GABA Antagonists; D058786:GABA-B Receptor Agonists; D018080:Receptors, GABA-B; C052329:phaclofen; D037342:Pertussis Toxin; D001418:Baclofen